Add Plausible analytics and say so in the privacy policy

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

layouts/partials/head.html

@@ -9,3 +9,9 @@
 <link rel="preload" href="{{ "fonts/inter-latin.woff2" | relURL }}" as="font" type="font/woff2" crossorigin>
 <link rel="stylesheet" href="{{ "css/fonts.css" | relURL }}">
 <link rel="stylesheet" href="{{ "css/style.css" | relURL }}">
+<!-- Privacy-friendly analytics by Plausible -->
+<script async src="https://plausible.federated.computer/js/pa-LB6kQDxarsX00LE4e5zh6.js"></script>
+<script>
+  window.plausible=window.plausible||function(){(plausible.q=plausible.q||[]).push(arguments)},plausible.init=plausible.init||function(i){plausible.o=i||{}};
+  plausible.init()
+</script>